It has been known in the railroad industry to connect together adjacent cars in a train by means of a so-called "standard coupler" and in more recent times to connect such adjacent cars together in a substantially semi-permanent manner using drawbars.
It is also known in the railway art to provide draft gear assemblies in a coupling arrangement to absorb at least a portion of the buff and draft forces which are generated and applied to the railroad freight cars during in-track operation of the train consist and to provide slack between cars so that a relatively long train of cars can be started into motion one car at a time.
More recently it has been the practice on railways to eliminate draft gear assemblies and to provide instead slackless systems for connecting adjacent cars by means of couplers or drawbars.
Furthermore, since the introduction of the more powerful diesel locomotive in the modern railroad industry, it has been discovered that the slack formerly required between adjacent cars in the older style coupling arrangements to enable a relatively low powered locomotive to start a train consist in motion one car at a time is no longer required. As a result, slackless coupling and drawbar assemblies have generally come into widespread use in the railroad industry as an arrangement for joining together the adjacent ends of a pair of railway freight cars in a train. It has been demonstrated that these slackless assemblies enable the buff and draft forces which are generated by in-track movement to be distributed through the car center sill member to all of the railway cars making up such train consist with less damage to both the freight car components and cargo.
It has now been found that operation of a slackless connection system can be improved if it is combined with a draft gear apparatus permitting limited longitudinal movement between the connecting pin of a slackless connection system and the center sill of a railway car to which it is connected when the system is under buff load. Such movement can be provided by compression of an elastomeric assembly which can absorb a predetermined level of buff load, established in part by the location of a rigid sill load member.
The elastomeric assembly can be prestressed to absorb a predetermined amount of buff loading before relative motion between the connecting pin and the railway car center sill occurs. The maximum load absorbed by the elastomeric assembly is a function of the initial prestress, the compression characteristics of the elastomer used and the distance through which the connecting pin is allowed to move before the rigid sill load member is contacted.
The connection system so constructed is effective to absorb all or a substantial portion of impact loads occurring during changes from draft to buff loads and reduces the deleterious effects of such loads on railway cars and cargo.